1. Field of the Invention
The present invention relates to testing of semiconductor wafers and, more particularly, to determining a relative concentration of defects and/or impurities in a semiconductor wafer.
2. Description of Related Art
During processing of a semiconductor wafer to form integrated circuits thereon, it is often desirable to detect a relative concentration of defects and/or impurities in the semiconductor wafer to determine if the concentration of defects and/or impurities in the semiconductor wafer is within acceptable tolerance(s). To this end, it is often desirable to detect whether the processing steps utilized to form the integrated circuits are causing changes in the concentration of defects and/or impurities in the semiconductor wafer.
Heretofore, measurements of the concentration of defects and/or impurities in a semiconductor wafer involved corona-based and/or CV-based measurements which require the presence of a relatively thick dielectric layer on the semiconducting material of the semiconductor wafer. This prerequisite prevented these tools from making measurements on the semiconducting material itself or on a semiconductor wafer having a relatively thin dielectric layer, i.e., a thickness of no greater than about 30 Angstroms.
Accordingly, what is needed, and not disclosed in the prior art, is a method and apparatus for determining the relative concentration of defects and/or impurities in a semiconductor wafer that either has no dielectric layer over the semiconducting material of the semiconductor wafer or has a relatively thin, i.e., no greater than 30 Angstroms, dielectric layer on the semiconducting material of the semiconductor wafer.